provides a backstory to Ryu's appearance and character as seen in the Dead or Alive series, being set two years before the first DOA game. Rachel is the leading female character, and tragic heroine of the game. She and her twin sister, Alma, are afflicted with a blood curse that turns humans into fiends. Believing that there is no cure for their condition, Rachel seeks to kill Alma to redeem her sister's soul. The relationship between the sisters and the Greater Fiend Doku, who cursed them, serves as a plot device to drive the game forward, with Rachel occasionally needing to be rescued by Ryu. Although not a player-controlled character in Ninja Gaiden, in a few sections of the Ninja Gaiden Sigma remake she is controllable. Two other characters assist the player in the game. Ayane, a young female ninja and one of the DOA regular cast members, acts as a guide throughout Ninja Gaiden by supplying advice and objectives to the player. Muramasa, a bladesmith, has shops scattered throughout the game world where players can purchase useful items and upgrades for Ryu's weapons. Muramasa also gives quests and relates back-stories and other crucial information; for example, he tells Ryu how he can obtain the item required to upgrade his Dragon Sword to its full potential. Players have the option to customize the appearance of player characters, with selectable costumes for Ryu and hairstyles for Rachel. Most of the enemies are fiends—humans changed into monsters by their blood curse. Three Greater Fiends lead their lesser brethren against Ryu, playing major roles in the game's plot: Alma, Rachel's sister, whose story forms a significant part of the game; Doku, Ryu's main antagonist, whose raid on Hayabusa village and theft of the Dark Dragon Blade comprise the main plot thread; and Marbus, lord of the fiend underworld who is responsible for the final set of challenges Ryu faces in the realm of the fiends before encountering the Vigoor Emperor. Story Ninja Gaiden'''s story spans 16 chapters, each beginning and ending with a cutscene. At the start of the game, the player takes control of Ryu as he infiltrates the Shadow clan fortress. Ryu is there to visit his uncle, the clan leader Murai. During their chat, Ayane delivers news of a raid on the Hayabusa village. Fighting his way back to his village, Ryu encounters Doku, who has killed the Hayabusa shrine